The present invention relates to a heat alarm device.
Heat alarm devices for sensing heat, for example from a fire, are well known in the art.
Typically such heat alarms comprise a body containing control and drive circuitry, a heat sensor extending from the body and a cage located around the heat sensor in a manner that allows free flow of air past the sensor. The cage is rigid and is typically made of such a size that it stands well clear of the sensor such that its thermal mass has minimum impact on the response of the sensor to a rise in ambient temperature.
The cage is necessary to present the heat sensor at a position removed from the large thermal mass of the electronics and body of the alarm, whilst also protecting the heat sensor from damage, and preventing the sensor (which will be attached to a source of electricity) being accidentally touched by anyone.
The sensor is generally centrally located so that the effect of the thermal mass of the body is substantially equal irrespective of the direction from which the heat originates (e.g. there is no heat shadow created by off-setting the sensor) and the protective cages are generally quite large relative to the sensor so that air can freely circulate around the sensor.